Quoting Trent W. Buck (trentbuck@gmail.com):
That shouldn't be necessary. ?dm should run .xsession by default, if there is one.
Be that as it may, I found out accidentally one day that disabling X11 session management very efficiently prevents an installed and configured DE from loading at all, i.e., absolutely nothing except for the configured window manager runs at X startup time. That may not be the right way to defang a DE, but it happens to work very well.
I guess, but I'd have thought it easier to
cd echo wmaker >.xsession chmod +x .xsession
Point taken about .xsession -- which obviously I'm going to have to look up and understand yet again. Back in dinosaur days, when I was dissembling the X infrastructure of early Slackware and Red Hat Linux boxen, I traced all of that ghod-awful maze of conffiles until, for one glorious moment, I held it all in my head, in all of its hideous glory. And was well and truly revolted. And then the moment passed, and I've forgotten much of it, rather like the mostly-recovered protegonist of an H.P. Lovecraft short story.